21 8 BACTERIA 



however, placed the matter on a much surer footing ; he has, 

 as we have seen, succeeded in separating a specific bacillus 

 from tuberculous material, with which he has been able to 

 produce tuberculosis with the utmost certainty, so that, 

 instead of dealing with comparatively large fragments of 

 diseased tissue, he has worked with particles so small that 

 they can only be distinguished with the aid of the best 

 microscope and the use of special methods of preparation. 

 This, of course, has cleared up many points which hitherto 

 have been very obscure, and, most important of all, it has 

 enabled us to determine the channels by which human beings 

 may become affected with the disease, especially in connec- 

 tion with the respiratory passages and by way of the 

 alimentary canal, and through wounds or damaged tissues. 



It has been demonstrated that in the sputum of patients 

 suffering from phthisis, in those cases where the softened 

 lung tissue is breaking down and is being expectorated, an 

 enormous number of tubercle bacilli may often be met with, 

 though they may be present in comparatively small num- 

 bers ; so frequently is this the case, that the presence (in 

 different numbers from day to day) of tubercle bacilli in 

 the sputum, or their absence, is relied upon as a diagnostic 

 feature by attention to which the physician is enabled not 

 only to determine the rapidity with which breaking down is 

 going on, but even to obtain very considerable assistance 

 in arriving at a decision as to whether a disease is tubercular 

 or not. 1 



Until quite recently not the slightest attempt has been made either to 

 prevent the diffusion of such sputum, or to disinfect it in any way, and it 

 has been said, with some considerable degree of truth, that a very large 

 quantity of virulent tuberculous material has been allowed to be freely dis- 

 seminated, with the result that it must have been the lot of many individuals 

 to contract tuberculosis by means of the inhalation of particles of dried 

 tuberculous sputum in which active tubercle bacilli or their spores were 

 necessarily entangled. That the sputum contained the elements which 



1 In making an examination of sputa for tubercle bacilli, the fact that 

 the bacilli are most numerous in the small yellow caseous points should 

 always be borne in mind. Such points should be carefully searched for, 

 crushed between two cover glasses, dried, stained, and examined. Single 

 bacilli may be found elsewhere, but masses can, as a rule, be found in these 

 disintegrating points only. It is only where disintegration has commenced 

 that any reliance can be placed on the numbers of tubercle bacilli as 

 affording any assistance in forming a diagnosis and prognosis. 



